When a user wants to utilize an IP telephone system, he or she installs a calling application, which is a software program for performing outgoing calls, incoming calls and audio communication, provided by a provider of IP telephone system in a personal computer or telephone terminal. Information such as user ID, display name, and profile for indicating the identity of a user are registered in the calling application. Skype can be taken as an example of the IP telephone system.
In recent years, a multi-user environment where a plurality of different user environments can be operated in parallel is used in an operating system of a personal computer. On each user environment, a software program such as a communication application is allowed to continue running in an independent manner. Windows XP® by Microsoft can be taken as an example of such a multi-user operating system. That is, in a state where a first user has logged on to Windows XP®, a second user can log on to Windows XP® without the need for the first user to log out from Windows XP®. The first and second users can continue running the software program on the respective user environments.
Japanese Patent Application Publication No. 2005-175722 discloses a system where a personal computer capable of communicating across a network is connected to a handset via a USB connection. In this system, a user using the handset performs IP telephone communication with a partner device on a network using a calling application installed in the personal computer.